In essence, projects planned for the coming year will continue work already in progress. Much effort will concentrate on perfecting the soft-agar technique for the growth of hematopoietic cells in vitro which we have begun to analyze on the ultrastructural level. This method will be used for the detection of a possible eosinopoietic factor in the serum of patients with eosinophilia and constitutes part of our program to elucidate the mechanism of eosinophilia. Other studies will use an animal model in which we are able to induce eosinophilia by tissue localization of various antigens. The supernates of sensitized lymphocytes derived from these animals will be used in transfer experiments again to detect the possible existence of an eosinophilopoietic factor. Other studies will deal with the histochemical localization of 5' nucleotidase, on normal lymphocytes and those of patients with chronic lymphocytic leukemia, since it has been shown by biochemical means that CLL lymphocytes are heterogeneous in this respect. It is hoped that further definition of the various subpopulations of these cells, in addition to the immunologic typing, will lead to a more rational approach to therapy.